PSAT Math Multiple-Choice Question 591: Answer and Explanation

Question: 591

The graph of the function below is given by which equation

• A. f(x) = 2x² - 2x - 4
• B. f(x) = 3x² - 6x - 7
• C. f(x) = x² + x - 3
• D. f(x) = x² - x - 6

Correct Answer: D

Explanation:

(D) Since the parabola has zeros at 3 and -2, it can be written in this way:

f(x) = (x - 3)(x + 2)

Use FOIL:

f(x) = x² - x - 6

Alternatively, you can set x = 0. Then see which of the choices results in a y-value of -6 since this is the y-intercept of the parabola based on the graph. Only choice (D) works:

f(x) = x² - x - 6

f(0) = 0² - 0 - 6 = -6

f(0) = -6